Intellisense in SSMS doesn’t work any more

In my last job Intellisense stopped working in SSMS and I just lived with it for years. When I came to a new office, it worked for a while, and then stopped one day. But it’s so much extra typing, I decided to try to fix it.

Here are the culprits, in order of ease-to-fix, ending with what I had to do :)